1. Field of the Invention
The present invention relates to methods of manufacturing solid-state image pickup devices and color image pickup devices using solid-state image pickup devices used for image pickup apparatuses such as digital cameras and to apparatuses for manufacturing the solid-state image pickup devices and the color image pickup devices.
2. Description of the Related Art
When images are captured using photographing apparatuses which include single-plate solid-state image pickup devices, only a single spectral sensitivity can be obtained. Thus, color photographing techniques, in which filters of different colors are provided for individual pixels and arranged in a predetermined pattern, are widely used. An image captured using such a technique exhibits a color mosaic pattern since each pixel represents only a single color in the image. However, an image having a region with a uniform color from predetermined neighboring pixels can be generated by interpolating color information on the neighbor pixels. This interpolation process is called a color separation process.
However, in this color separation process, individual colors are discretely sampled. Thus, when a photographed image contains a high-frequency component that exceeds a Nyquist frequency, aliasing (folding of high-frequency components onto low-frequency components) occurs, which decreases the color determination accuracy.
To address this problem, techniques have been developed for suppressing the generation of a false color in an image by reducing regularity (periodicity) in an array of color filters. For example, in the pseudo-random Bayer pattern, which has been developed by FillFactory (now Cypress Semiconductor Corporation), a three-color G-checkered pseudo-random array is provided in which green (G) filters are arranged in a checkered pattern, and red (R) filters and blue (B) filters are pseudo-randomly arranged in the remaining blocks (checks) of the checkered pattern.
In addition, Japanese Unexamined Patent Application Publication No. 2000-316169 by Yoshida Hideaki, entitled “Color Image Pickup Element and Device” discloses a six-color random array. In this array, pixels are arranged under the condition that a target pixel is adjacent to pixels (filters) of six colors including the color of the target pixel, at the four sides or the four corners of the target pixel.
Further, in European Patent Application Publication No. 0,804,037(A2) by Dr. Mutze Ulrich, entitled “Process and System for Generating a Full Color Image or Multispectral Image from the Image Data of a CCD Image Sensor with a Mosaic Color Filter”, a 3×3 periodic filter array composed of filters of five color components and a pseudo-random array are described.
In the pseudo-random Bayer array of FillFactory (Cypress Semiconductor Corporation), R filters and B filters are arranged in a pseudo-random pattern. However, the repetition rate of the R-B pseudo-random pattern is high. Thus, this pseudo-random Bayer array can cause some change relative to the Bayer array in a position at which a false color is generated in the spatial frequency domain, and thus have little substantial effect on reducing the occurrence of a false colors in an image. On the other hand, the random arrays disclosed by Yoshida and Mutze have more randomness than the pseudo-random Bayer array of FillFactory, and thus an effect on the reduction of the occurrence of false colors can be expected. However, the random arrangements of filters of all color components in these random arrays lead to deterioration of resolution, compared with a Bayer array disclosed in Japanese Patent No. 2931520, in which correlation processing can be executed, and the pseudo-random Bayer described above.
In order to suppress the generation of false colors, color filters of at least one predetermined color component need to be randomly arranged. In order to increase the reproducibility of resolution, color filters of at least one predetermined color component need to be regularly (periodically) arranged.
In addition, in order to interpolate a color component that is not included in a target pixel from neighboring pixels, it is necessary that all colors are arranged in the neighborhood of the target pixel, even if filters of a predetermined color component are randomly arranged.
Such a color filter array that fulfills the necessities described above has yet to be existed.